In general, an ingot growth apparatus using a Czochralski crystal growth process is configured such that solid raw material, such as polysilicon (or gallium arsenide) and dopant, is introduced (supplied)) into a crucible mounted in a hot zone, the solid raw material is heated and melted by an electric heater to form silicon hot melt, and a single crystal seed is slowly rotated and seeded in a state in which the single crystal seed is in contact with the silicon hot melt so as to obtain single crystal ingot having a predetermined length and a predetermined diameter.
Chunk polysilicon and granular polysilicon are used as polysilicon, which is raw material for ingot growth, and a predetermined amount of boron or phosphorus is generally used as dopant. Boron is used for P-type ingot growth, phosphorus is used for N-type ingot growth.
The above-mentioned raw materials are in a solid state. In order to melt the raw materials into silicon hot melt, therefore, chunk polysilicon is stacked in a dome shape in a state in which the dopant is put in the crucible. Even when chunk polysilicon, granular polysilicon, and dopant are filled and melted in the crucible, the volume of the silicon hot melt equivalent to gaps formed in the chunk polysilicon is reduced.
In addition, the silicon hot melt is gradually reduced according to the growth of an ingot with the result that the level of the silicon hot melt is lowered. In this case, the change in level of the silicon hot melt is detected using a distance measurement mechanism, and the crucible is moved upward using a lifting mechanism according to the detected change in level of the silicon hot melt such that the level of the silicon hot melt can be uniformly maintained. However, accurate control is difficult, and the supply of a fixed amount of raw material is not easy. Consequently, the diameter of the grown ingot is not uniform, and concentration of the dopant is changed in a direction in which the ingot is seeded. As a result, there occurs a so-called segregation phenomenon in which the quality of the ingot is not uniform.
In order to grow an ingot having a desired diameter and a desired length while uniformly maintaining quality of the grown ingot, therefore, it is necessary to quantitatively supply an amount of ingot raw material (polysilicon and dopant) equivalent to the volume reduced according to ingot growth (or volume required for ingot growth).